This invention relates to a method for alleviating leaching of chromium and/or lead compounds from incinerated waste materials.
Some waste materials contain heavy metals, in particular compounds of chromium or lead. Examples of such waste materials are spent olefin polymerization catalysts which contain chromium (generally in the +6 valence state) on inorganic support materials (such as silica). When these waste materials are burned in an incinerator, the formed ash frequently contains the chromium and/or lead impurities as water-soluble compounds. Thus, when the ash is disposed of in a landfill, the chromium and/or lead impurities can gradually leach from the ash and contaminate the ground water. The present invention is directed to alleviating the leaching of chromium and/or lead impurities from incinerated waste materials.